1. Field of the Invention
The present invention relates generally to a video display appliance, and more particularly to a brightness control apparatus and method that can lengthen the lifetime of a lamp and reduce a power consumption for a video display appliance using the lamp such as a projector and a projection television receiver (TV).
2. Description of the Related Art
Recently, as the development of large-sized ultra-thin displays becomes active due to the limitations of screen size of the existing TVs, projection type display systems have notably been developed. Additionally, the spread of projectors and projection display appliances using a display device such as a CRT (Cathode Ray Tube), an LCD (Liquid Crystal Display), an LCoS (Liquid Crystal on Silicon), a DLP (Digital Light Processing), etc., has abruptly been increased.
The LCD, which is one of flat-panel display devices, has a superior visibility, a small average power consumption, and a small amount of heat generation in comparison to the CRT, and thus has been spotlighted as the next-generation display device of a cellular phone, a computer monitor, a TV, etc., along with a PDP (Plasma Display Panel) and an FED (Field Emission Display).
The projection display appliance having the LCD as its display device is a video display system that emits the three primary colors of red, green and blue, projects and enlarges an image using a projection lens and a reflecting mirror to form the final image on a screen.
The LCD has the structure in that a liquid crystal material is injected between two thin surface-processed glass plates having electrodes formed thereon, and operates to display an image by producing light and darkness through the change of arrangement of liquid crystal molecules due to the voltage difference between the electrodes. Because the LCD panel itself cannot emit light, a light source such as a lamp is required in order for a user to visually recognize the image or text displayed on the LCD panel.
In driving the LCD panel, a dimmer mode (i.e., a lamp power saving mode) may be performed to lengthen the lifetime of the light source. This lamp power saving mode is to lower the brightness of the lamp by supplying the lamp with a power that is smaller than that required for the maximum brightness of the lamp if the bright light is not required for the display, for example, in the dark room or in the case that a movie is displayed on the LCD panel.
By lowering the brightness of the lamp, the power consumption is reduced and the lifetime of the lamp is lengthened. Practically, in the case of viewing a movie through a projector in the room, the display screen is so bright as to dazzle to the user's eyes, and the user may use the lamp power saving mode. If the lamp power saving function is not provided in the display appliance, the user may adjust the display brightness using a menu for adjusting the brightness.
For the purpose of simply lowering the display brightness, it is much more effective in power consumption and lifetime of the lamp to use the lamp power saving mode in comparison to the lowering of the brightness value using the menu for adjusting the brightness. However, on the ground that users think it much trouble to use the lamp power saving mode or do not know what the lamp power saving mode itself is for, the lamp power saving mode may not be properly used.
If the display brightness is adjusted to dark in a state that the operating video display appliance is not in the lamp power saving mode, the power consumption is not reduced and the lifetime of the lamp is not lengthened in comparison to the state that the video display appliance operates in the lamp power saving mode.